1. Field of the Invention
This invention relates to a dielectric ceramic composition which possesses a high dielectric constant and a high unloaded Q and exhibits stable temperature properties.
2. Description of the Prior Art
In dielectric resonators and dielectric substrates used in signal circuits operating in the high frequency region, such as the microwave and millimeter wave regions, dielectric ceramics possessing a high dielectric constant and a high unloaded Q and exhibiting stable temperature properties find utility.
Heretofore, as dielectric ceramics of this kind, dielectric ceramics of the Ba(Zn-Ta)O type [Japanese Patent Publication SHO 59(1984)-48,484], the Ba(Zn-Nb)O type [Japanese Patent Publication SHO 59(1984)-48,483], the Ba(Zn-Ta-Nb)O type [Japanese Patent Publication SHO 59(1984)-23,044], the Ba(Mg-Ni-Ta)O type [Japanese Patent Application Disclosure SHO 60(1985)-216,407], and the Ba(Mg-Co-Ta)O type [Japanese Patent Application Disclosure SHO 61(1986)-8,804]have been proposed.
The dielectric ceramics of the compositions disclosed in the three Japanese Patent Publications mentioned above have a high dielectric constant on the order of 30 to 40 and yet offer a small unloaded Q of about 5,000 in the high frequency region of about 10 GHz. The dielectric ceramics of the compositions disclosed in the two Japanese patent application disclosures mentioned above indeed have a large unloaded Q of about 8,000 and yet offer a low dielectric constant on the order of 25. Thus, they have a problem that they do not fulfill the requirement for a higher unloaded Q and a larger dielectric constant which the dielectric ceramic articles used in communication devices are expected to possess in keeping pace with the gradual advance in performance of such communication devices in recent years.